This is somewhat addressed in our Getting Started document, the relevant section below. It’s not exactly what you describe, but the take-home is the same: don’t use HR for high intensity intervals, use Pace or Power.
Q: With high-intensity short Zone 4 and 5 intervals, my heart rate can’t “catch up”.
A: This is addressed in our documents Understanding Your 80/20 Run Plan and Understanding Your 80/20 Triathlon Plan. Because HR is a lagging indicator, Pace and Power are more reliable methods at high intensities. Absent Pace and Power, RPE should be used for Zone 4 and 5. This issue can also be resolved by using the 80/20 Run and Bike Zones Garmin App, where you can have both real-time HR and your custom 80/20 Pace or Power zones displayed on your device at the same time.